In JFETs (junction field effect transistors) the extension of a depletion region of a reverse-biased pn-junction modulates the cross-sectional area of a channel region through which a load current controlled by the JFET passes. Since minority charge carrier storage effects influence the operation of JFETs only to a low degree, JFETs can be used in high speed applications. It is desirable to provide JFETs with improved device characteristics.